1. Field of the Invention
The present invention relates to a multi-layer information storage medium and an information apparatus.
2. Description of the Related Art
Known optical disks are information storage media having a sector structure. Optical disks can be generally classified into three types, depending on their characteristics. A first type is a read-only disk, which carries data that has been recorded in the form of bumps and dents on the disk, such that the user cannot record any new data. A second type is a write-once disk, which includes a recording film composed of an organic dye or the like, such that a recording is possible only once in each sector. A third type is a rewritable disk, which includes a recording film composed of a phase-change material or the like, such that a recording (rewriting) is possible a plurality of times.
In recent years, audio/video data (hereinafter referred to as “AV data”) of audio, video, etc., is broadcast or distributed in digital form, thus leading to a need for optical disks having higher densities and larger capacities. In order to obtain an increased storage capacity, it is effective to employ a plurality of recording layers. For example, in the case of a DVD read-only disk, two recording layers are formed in each optical disk, whereby its capacity is increased about twofold.
The increase in the capacities of optical disks has also made them available for video recording, e.g., DVDs. On the one hand, data for computer data recording (hereinafter referred to as “PC data”) does not tolerate even small errors, and therefore requires highly reliable recording. Examples of PC data include data files, file management information, and program management information. On the other hand, AV data for video recording and/or audio recording needs to be recorded in real time as the data comes in continuously. The reproduced video and/or audio may contain some disturbances so long as they are tolerable to the human senses, and therefore AV data does not require as much data reliability as does a computer data recording file. However, it is important that recording of AV data can proceed without interruptions. Thus, different abilities are expected of a storage device for PC data recording and a storage device for AV data recording: the former requires a high reliability even if it may be more time-consuming, whereas the latter requires an ability to achieve continuous recording.
Referring to FIG. 1, the principle of data reproduction from an optical disk having two recording layers will be described. The illustrated optical disk includes a pair of transparent substrates having spiral track grooves formed thereon, the transparent substrates supporting two recording layers. The transparent substrates are attached together, via a transparent photocuring resin which is filled in the interspace between the two recording layers, thus constituting one optical disk.
For convenience, the recording layer which is located at a longer distance from the data-reading surface of the optical disk will be referred to as the “first recording layer”, whereas the recording layer with a shorter distance therefrom will be referred to as the “second recording layer”. The thickness and composition of the second recording layer are adjusted so that the second recording layer is partly reflective and partly transmissive with respect to incident light. The thickness and composition of the first recording layer are adjusted so that the first recording layer reflects all of the incident light. By bringing an objective lens (for converging laser light) so as to be close to or away from the optical disk, a beam spot (focal point) of laser light can be selectively converged on the first or second recording layer.
FIG. 2 shows an area-layout of a recording layer 21 of a conventional rewritable optical disk. In the recording layer 21 shown in FIG. 2, a lead-in area 22 includes a disk information area 26 and a defect management area 27 (hereinafter abbreviated as “DMA”) formed therein. A lead-out area 25 also includes a defect management area 27 formed therein. Spare areas 23 are provided between the lead-in area 22 and a user data area 24, and between the user data area 24 and the lead-out area 25.
The disk information area 26 stores parameters which are necessary for performing data recording/reproduction for the optical disk, and information concerning physical properties of the optical disk.
The defect management areas 27 and the spare areas 23 are areas which are provided for realizing defect management. Under defect management, any sector in the user data area 24 for which proper recording/reproduction cannot be performed (thus called a “defective sector”) is replaced by another sector which is in good condition.
Each spare area 23 is an area containing sectors with which defective sectors are to be replaced (such sectors will be generally referred to as “spare sectors”, and any spare sector which has actually replaced a defective sector will be referred to as a “replacement sector”). In a DVD-RAM, spare areas 23 are provided at two positions, i.e., the inner periphery side and outer periphery side of the user data area 24, and the size of the spare area 23 that is provided at the outer periphery side is increasable so as to accommodate an unexpected increase in the defective sectors.
Each defect management area 27 includes: a disk definition structure (DDS) 28 for retaining a format concerning defect management, including management of the size and locations of the spare areas 23; and a defect list (DL) 29 which is a listing of positions of defective sectors and positions of replacement sectors corresponding thereto. In many optical disks, for robustness concerns, the same content is recorded in duplicate in each of the defect management areas 27 at the inner periphery side and the outer periphery side, thus resulting in quadruplet recording of the aforementioned elements (see, for example, Japanese Laid-Open Patent Publication No. 2003-288759).
On the other hand, in a write-once medium, any piece of information that has once been written cannot be erased. Due to such characteristics, instead of overwriting any previously-recorded information, new information is always appended in a new position (“additional write”). Therefore, a write-once medium contains management information which is different from that of a rewritable-type medium.
FIG. 3 shows an area-layout of a recording layer 301 of a DVD-R as a conventional write-once optical disk. The recording layer 301 shown in FIG. 3 includes, from the inner periphery side toward the outer periphery side, an R-information area 302 (hereinafter abbreviated as “R-Info”), a lead-in area 303, a user data area 304, and a lead-out area 305.
The lead-in area 303 includes a disk information area 320 formed therein.
The R-Info 302 is an area which is unique to write-once disks. The R-Info 302 includes a recording management area 310 (hereinafter abbreviated as “RMA”).
The RMA 310 is composed of recording management data 311 (hereinafter abbreviated as “RMD”), each of which represents a recording status of the disk. By acquiring the latest RMD 311, it becomes possible to acquire addresses at which additional writes can be performed, etc.
In the case of a DVD+RW, the aforementioned information can be obtained by referring to the FDCB (Format Disc Control Block) information. In the case of a DVD+R, the aforementioned information can be obtained by referring to the SDCB (Session Disc Control Block) information.
FIG. 4 shows an area-layout of a recording layer 401 of a conventional write-once optical disk which contains defect management information. The recording layer 401 shown in FIG. 4 includes, from the inner periphery side toward the outer periphery side, a lead-in area 402, a spare area 403, a user data area 404, another spare area 403, and a lead-out area 405.
The lead-in area 402 includes a disk information area 420, a defect management area 430, and a temporary disk management area 440 (hereinafter abbreviated as “TDMA”) formed therein. The lead-out area 405 includes a defect management area 430. The spare areas 403 are located between the lead-in area 402 and the user data area 404, and between the user data area 404 and the lead-out area 405.
In the case of a write-once optical disk, recording to DMA can only be made once, too. Therefore, by using any method similar to that for a rewritable optical disk, it is impossible to ensure that the latest defect management information is always recorded in a DMA which is at a predetermined position. This is the reason why the TDMA is provided, which realizes compatibility with a rewritable-type optical disk.
The TDMA 440 is composed of N temporary disk management structures 441 (hereinafter abbreviated as “TDMS”), where N is a positive number equal to or greater than one. The TDMS 441 is an area for temporarily recording defect management information that have been updated before the write-once optical disk receives a finalization (i.e., conversion of a write-once optical disk to a data structure which is compatible with rewritable optical disks, which involves recording the content of the latest TDMS 441 in DMA form). The TDMS 441 is composed of: a temporary defect list (hereinafter abbreviated as “TDL”) 442, which is a listing of positions of defective sectors and positions of replacement sectors corresponding thereto; and a temporary disk definition structure (hereinafter abbreviated as “TDDS”) 443, which includes temporary defect list beginning position information (i.e., information of a beginning position of the temporary defect list 442) and the like.
In the disk information area (26 in FIG. 2; 320 in FIG. 3; 420 in FIG. 4), information is recorded in the form of pits (bumps and dents). Alternatively, before disk shipment, for example, a method which is similar to the method of performing a recording to the data area is carried out to make pre-recordings in the disk information area.
The defect management information (DDS and DL, or TDL and TDDS) and the recording management data (RMD, FDCB, or SDCB) are to be recorded by an optical disk drive or the like after disk shipment.
Japanese Laid-Open Patent Publication No. 2004-206849 discloses a multi-layer information storage medium comprising a plurality of recording layers, and teaches to provide management information in a specific recording layer.
A write-once or rewritable multi-layer optical disk having a plurality of recording layers has a problem in that a recording layer at a shorter distance from the data-reading surface has a lower reliability when scratches, fingerprints and/or dust exist on the disk surface, possibly making data reproduction from the optical disk impossible. This is because, as shown in FIG. 5, the scratches, fingerprints and/or dust on the disk surface greatly affect the reproduction light.
For example, there is a problem in that, if the defect management information (DDS and DL, or TDL and TDDS) or a replacement sector cannot be reproduced, it is impossible to reproduce the user data which is recorded on the information storage medium.
The recording management data (e.g., RMD, FDCB, SDCB) is important management information which indicates the recording status of the optical disk, as described above. Therefore, if the recording management data cannot be reproduced, it becomes impossible to perform any additional writes to the optical disk, so that the advantage of the disk's large capacity is lost. The loss is increased as the storage capacity of the disk becomes larger.
If the file management information cannot be reproduced, it becomes impossible to access file data itself, so that the file data is no longer useable. There is also a problem in that a data file (e.g., a data file produced by a word processor) may become entirely unreadable even when only a portion thereof cannot be read.
Japanese Laid-Open Patent Publication No. 2004-206849, supra, discloses providing a management information area in a specific recording layer, but teaches that a recording layer which is in a position where there is minimum unfavorable influence from the tilt of an optical disk should be selected as such a specific recording layer. The unfavorable influence from the tilt of an optical disk is known to increase at deeper depths from the data-reading surface. Therefore, based on the teachings of the aforementioned publication, one would conclude that it is preferable to provide any management information area in a recording layer that is the closest to the data-reading surface. However, as described above, there is a problem in that the influence of the scratches, fingerprints, etc., on the disk surface would increase as the distance from the data-reading surface to the recording layer becomes shorter.